JP2003209350A - Electronic circuit device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve Pb-free solder mounting when an IC with a bump is mounted and then solder mounted in an electronic circuit device. <P>SOLUTION: As the solder used in a solder mounting step, a solder containing any of an Sn-Zn or Sn-Zn-Bi alloy having a melting point near 200°C or an Sn-Bi alloy having a melting point near 140°C as a main component is used. Thus, as compared with the case when a conventional solder containing an Sn-Pb eutectic alloy as a main component is used, the melting point and a reflowing temperature can be lowered or can be restricted to a rise of the lowest limit. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bare chip such as a driver IC, a memory IC, a controller IC used in a portable device, an electronic notebook or a liquid crystal display device, and a soldering surface mounting component. The present invention relates to an electronic circuit device and a manufacturing method thereof.

[0002]

2. Description of the Related Art The following is known in a conventional method for manufacturing an electronic circuit device.

The first step of joining a bump-formed IC on a flexible substrate in a face-down manner is a bump electrode, which is formed of Au (gold) on the IC electrode, and a conductor pattern on the flexible substrate. The surface of which is plated with Au is used for anisotropic conductive adhesive, contact between insulating adhesive and electrode (mechanical contact), conductive adhesive + resin sealing, or between metals (Au: Au). Spread +
Join by resin sealing or the like.

In addition, a conductor pattern surface of a flexible substrate plated with Sn (tin) is used as an intermetallic (A
In some cases, they are joined by diffusion of u: Sn) + resin sealing.

The above-mentioned anisotropic conductive adhesive, insulating adhesive,
The main components used for resin sealing include resins such as epoxy resins and acrylic resins.

The second step of joining various surface mounting parts is performed after the end of the first step.

The bonding material is generally Sn-37 wt% P
A solder having a eutectic composition of b (lead) and a melting point of about 183 ° C. is used. At the time of mass production, solder paste in which flux and solder balls are kneaded is printed on a substrate, surface mounting components are mounted by a chip mounter or the like, and they are joined by heating, melting and resolidifying in a reflow furnace. The maximum temperature of the component during reflow is set to about 220 ° C with a margin of about 40 ° C to the melting point.

In recent years, the melting point of Pb-free is 220.
In some cases, Sn-Ag-Cu based solder having a temperature of around 0 ° C is used. In this case, the maximum temperature of parts during reflow is 250
~ 260 ° C is required.

[0009]

However, the conventional techniques have the following problems. When using Pb-containing solder, Pb is a highly toxic metal and causes environmental pollution.

When Sn-Ag-Cu based solder is used, the following problems (1) to (3) occur. (1) Since the melting point is high and the reflow temperature is high,
In some cases, the thermal stress during reflow increases, the IC joint portion itself and the sealing resin deteriorate, and connection failure, strength reduction, reliability deterioration, etc. may occur. In addition, the performance of ICs and surface mount components may deteriorate. (2) The conventional reflow furnace for Sn-Pb-based solder may be unusable due to insufficient capacity. (3) Since the precious metal Ag is included, the material cost of the solder increases. The present invention solves the above problems, and
I on a flexible substrate without using
It is to realize the joining of C and surface mount components.

[0011]

As means for solving the above problems, in the present invention, the first step of face-down bonding of ICs having bumps formed thereon and the bonding of various surface mounting components are performed on a flexible substrate. In the method for manufacturing an electronic circuit device including the second step, the bonding material used in the second step is a Sn—Zn-based or Sn—Z-based material having a melting point of about 200 ° C.
It has been decided to use a solder whose main component is either an n-Bi-based alloy or a Sn-Bi-based alloy having a melting point of about 140 ° C.

Therefore, the melting point and the reflow temperature are lowered, or the increase is kept to a minimum, as compared with the case of using the conventional solder containing Sn-Pb eutectic alloy as a main component without containing Pb. It becomes possible. Also, Ag
Since it does not contain Sn, the cost of the solder material can be suppressed as compared with the Sn-Ag-Cu system.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings.

1 to 4 schematically show a method of manufacturing a drive circuit block for a small display element, which is a kind of electronic circuit device according to the present invention.

FIG. 1 is a top view showing a first step of a method of manufacturing an electronic circuit device according to the present invention, and FIG. 2 is a sectional view showing a first step of a method of manufacturing an electronic circuit device according to the present invention. . The substrate 1 is a flexible substrate in which copper foil conductor wiring (not shown) is formed on polyimide, and the wiring surface in the vicinity of the joint is Sn-plated.

The IC 2 has about 100 to 1000 Au bumps (protruding electrodes) formed on the electrodes of the bare chip, and the electrodes (not shown) of the substrate 1 and the bumps of the IC 2 are aligned to each other. By thermocompression bonding at a temperature of 500 ° C. and a load of several to 100 g per electrode, A
u and Sn diffuse between the metals, and the IC joint portion 4 is formed.

In addition to this, the IC 2 and the substrate 1 are joined together.
Various methods such as anisotropic conductive adhesive, contact between insulating adhesive and electrode (mechanical contact), conductive adhesive + resin sealing, or diffusion between metals (Au: Au) + resin sealing It is possible to select the optimum one for the conductor wiring of the substrate 1, the surface treatment thereof, and the specifications of the bumps.

After the formation of the IC joint portion 4, the substrate 1, the IC 2 and the substrate I, I, are provided to protect and reinforce the IC joint portion 4 and the semiconductor element.
The sealing resin 3 is supplied to the gap of the C-bonding portion 4 and its periphery and cured.

The sealing resin 3 is supplied by being applied to the periphery of the IC 2 in a liquid state, and is supplied by flowing to the IC 2
Is filled in the gap between the substrate 1 and the substrate 1 and around the IC 2,
It cures by V, light, anaerobic condition, reaction of 2 liquids, etc. alone or in combination. An epoxy resin, an acrylic resin, or a combination of both resins is used as the sealing resin 3, and there are cases in which additives, fillers, etc., which meet various characteristics such as thermal expansion, viscosity, and curing conditions, are included. In addition, heat may be applied to the substrate 1 and the resin itself in order to adjust the viscosity during coating.

FIG. 3 is a top view showing a second step of the method for manufacturing an electronic circuit device according to the present invention, and FIG. 4 is a sectional view showing a second step of the method for manufacturing an electronic circuit device according to the present invention. .

Electrodes (not shown) for mounting one 6-pin SOP 5 and six chip resistors 6 are formed around the IC 2 mounting portion of the substrate 1.

Next, a solder paste containing flux is supplied on the electrodes by a dispensing method or a printing method. In addition to the solder paste method, solder is supplied to the conductor wiring side, the lead terminal side or the IC electrode side by electroplating,
There are cases in which electroless plating, hot dip plating (solder coating), solder ball mounting, and other methods that are supplied are used alone or in combination, and when thread solder is supplied manually or automatically.

After the solder is supplied, the electronic parts of the SOP 5 and the chip resistor 6 are mounted on the board-side electrodes. In the case of a solder supply method other than the method using solder paste, an electronic component may be supplied using an adhesive or the like before the solder supply.

After mounting the electronic parts, they are heated and melted by hot air, infrared rays, laser, thermocompression bonding, soldering iron, etc., alone or in combination, and then re-solidified by natural or forced cooling. 6
Solder joints 7 are formed between the electrodes.

In this case, it is possible to suppress the deterioration of the flux and the oxidation of the solder surface by making the atmosphere in the joint part nitrogen-replaced so that the oxygen concentration is low.

The drive circuit block for the small display element is completed here. Then, the display module is completed by joining the display element such as the LCD and the drive circuit block.

The solder used in this process has a melting point of 2
A solder containing a Sn-Zn-based alloy, a Sn-Zn-Bi-based alloy near 00 ° C, or a Sn-Bi-based alloy near a melting point of 140 ° C as a main component is used. The maximum temperature of parts when heated in a reflow furnace is Sn-Zn system, as well as Sn-Z.
In the case of a solder containing an n-Bi alloy as a main component, it was stable at about 220 ° C, which is comparable to that of a conventional Sn-Pb eutectic solder, and in the case of a solder containing an Sn-Bi alloy as a main component, it was stable at about 180 ° C. It becomes possible to realize joining.

As a result, without containing Pb,
The melting point and the reflow temperature are reduced as compared with the case of using a solder containing a conventional Sn-Pb-based eutectic alloy as a main component.
Or it is possible to keep the rise to the minimum.

Therefore, deterioration of the IC bonding portion 4 and the sealing resin 3 created in the first step can be prevented, and the bonding quality of the IC 2 can be secured and maintained. Further, since the conventional reflow furnace for Sn-Pb solder can be used and the material does not contain expensive Ag, the cost of the solder material can be suppressed as compared with the Sn-Ag-Cu solder.

Sn-Zn based solder is Sn-9 wt% Zn.
It is based on a eutectic (melting point 198 ° C), and Zn is 7-
A range of 10% by weight is preferable.

Outside of this range, Zn has a wide solid-liquid coexistence range or an excessively high solidification start temperature, and adversely affects strength and reliability.

Table 1 shows the reliability of the Sn--Zn type solder tested by changing the composition of Zn, and shows the results of the temperature cycle test of -40.degree. C. and 125.degree.

The number of temperature cycles until the bonding strength was 50% or less of the initial value was examined.

From Table 1, it can be seen that Zn is preferably in the range of 7 to 10% by weight.

[0035]

[Table 1]

Fe, Ni, Co, Au, Ag, Cu, Mn, Ti, for improving the properties such as wettability, strength, reliability, etc.
Cr, Zn, Al, B, As, Se, Te, Ga, G
It is also possible to add a small amount of e, P or the like.

Sn-Zn-Bi solder is Sn-Zn.
Bi is added in order to improve the wettability of the system solder and to lower the melting point. Zn is 7 to 10% by weight and Bi is 1 to 9%.
The range of weight% is good.

If Bi is less than this range, it is ineffective, and if it is more than this range, it is too brittle and the reliability is greatly reduced.

Table 2 shows the wet spread of Sn-Zn-Bi solder when Bi was added to 92% Sn-8% Zn. The wet spread test method was JIS Z.
According to 3197.

From Table 2, it is understood that the effect is obtained when Bi is added in an amount of 1% by weight or more.

[0041]

[Table 2]

Table 3 shows the results of examining the reliability of the Sn-Zn-Bi type solder when Bi was added to 92% Sn-8% Zn in the same test as above.

From Table 3, it can be seen that Bi is preferably added in an amount of 9% by weight or less.

[0044]

[Table 3]

As can be seen from Tables 2 and 3, Bi is 1
If it is less than 10% by weight, no effect is obtained, and if it is more than 9% by weight, it is too brittle and the reliability is greatly reduced.

It is also possible to add a small amount of other components in order to improve properties such as wettability, strength, reliability and the like.

Sn-Bi solder is Sn-58 wt% B
Based on i eutectic (melting point 139 ° C), Bi is 3
A range of 0 to 72% by weight is preferable.

When Bi is outside this range, the solid-liquid coexistence range becomes wide, or the solidification start temperature becomes too high, and when it is too large, strength and reliability are adversely affected.

Table 4 shows the reliability of Sn-Bi type solders tested by changing the composition of Bi. A temperature cycle test of -40 ° C and 100 ° C was carried out until the bonding strength was 50% or less of the initial value. The number of temperature cycles was investigated.

From this, it is understood that Bi is preferably in the range of 30 to 72% by weight.

[0051]

[Table 4]

In order to improve strength and reliability, 0.1-3.
Up to 0% by weight Ag may be added.

Other components may be added to improve properties such as strength and reliability.

The Pb-free solder of the present invention means a solder containing 0.1% by weight or less of Pb as an unavoidable impurity.

The above-described embodiment according to the present invention shows a typical manufacturing method and configuration. The shape, the number, the mounting position, the size, and the combination of each component / member other than the solder used for joining are as follows. It can be set arbitrarily according to the product specifications.

The substrate is not only a polyimide base but also a PE.
There is a case where a conductor wiring of copper, aluminum, gold, silver, nickel, etc. is formed on the base material such as T, and further, on the conductor wiring, preflux, solder plating, gold plating, Treatments such as tin plating, palladium plating, nickel plating, silver plating, and chrome plating may be used alone or in combination.

As the bumped IC, a wafer level package or a chip size package may be used in addition to the bare chip, and a plurality of chips may be mounted.

As the electronic parts to be soldered, various parts and various specifications such as QFP, BGA, transistor, diode, capacitor, thermistor, crystal, etc. may be used in addition to SOP and chip resistor.

[0059]

As described above, according to the present invention, even when the lead-free solder is mounted after mounting the bumped IC, it is possible to prevent the deterioration of the resin component used for IC bonding, The reflow furnace for Sn-Pb type solder can be used, and the cost of the solder material can be suppressed.

[Brief description of drawings]

FIG. 1 is a first method of manufacturing an electronic circuit device according to the present invention.
FIG.

FIG. 2 is a first method of manufacturing an electronic circuit device according to the present invention.
FIG.

FIG. 3 is a second method of manufacturing an electronic circuit device according to the present invention.
FIG.

FIG. 4 is a second method of manufacturing an electronic circuit device according to the present invention.
FIG.

[Explanation of symbols]

1 ... Substrate 2 ... IC 3 ... Sealing resin 4 ... IC junction 5 ... SOP 6 ... Chip resistance 7 ・ ・ ・ Solder joint

Claims (5)

[Claims] 1. In an electronic circuit device in which an IC having bumps formed thereon and various surface mounting components are mounted on a flexible substrate, the flexible substrate and the various surface mounting components are bonded by Sn—Zn system, Sn-Zn-Bi
An electronic circuit device, characterized in that it is made of a solder whose main component is either a Sn-based alloy or a Sn-Bi alloy. 2. The Sn—Zn alloy is 7.0 to 10.
The electronic circuit device according to claim 1, wherein the electronic circuit device is an alloy containing 0 wt% Zn and the balance Sn as main components. 3. The Sn—Zn—Bi alloy is 7.0 to 7.0.
The electronic circuit device according to claim 1, wherein the alloy is an alloy containing 10.0 wt% Zn, 1.0 to 9.0 wt% Bi, and the balance Sn as main components. 4. The Sn—Bi alloy is 30.0 to 7
2. The electronic circuit device according to claim 1, wherein the alloy is an alloy containing 2.0 wt% Bi and the balance Sn as a main component. 5. A first step of joining ICs having bumps formed face down on a flexible substrate, and a second step of joining various surface mounting parts on the flexible substrate, the second step The bonding material used in the step is Sn-
A method of manufacturing an electronic circuit device, which is a solder containing a Zn-based, Sn-Zn-Bi-based, or Sn-Bi-based alloy as a main component.